It is known to provide several rows of vanes which are orientable relative to the housing of the turbojet compressor. Such vanes may be pivoted during operation of the engine. Their arched airfoil swivel relative to the primary flow which they cross, which allows their action to be adapted according to the engine speed and flight conditions. The operating range is thus extended.
These vanes are equipped with control rods mounted so as to pivot in openings through the external casing of the compressor. The free ends of the control rods are extended laterally by control levers which are themselves connected to a control ring. Actuators allow the rings to be driven in rotation to incline the levers and hence orient the vanes. The actuators may be controlled as a function of sensors or of different operating parameters of the turbomachine.
The performance of the compressor depends on the precision of angular positioning of the vanes relative to the casing. To this end, the coupling between the control rod and the lever of a vane must be precise as well as having to tolerate significant torque levels. The installation setting of the orientation between the control shaft and the lever must be particularly precise.
Document US2010/0166540 A1 discloses a turbomachine for an aircraft equipped with a compressor section. The compression section comprises several rotor vanes and several stator vanes arranged upstream of the rotor vanes. The compression section comprises a variable geometry thanks to the presence of pivoting stator vanes, which allows modification of the pressure and speed of the fluid supplied to the rotor vanes. The pivoting vanes each comprise a journal extended by a control lever. These control levers are connected to a common actuating ring which allows the assembly of the row of pivoting vanes to be controlled by simple rotation of the actuator ring. Also, each lever has a pincer form engaged with the associated vane, which limits the mechanical play harmful to the accuracy of control. However, mechanical play persists at the control ring. Also, the rotation of the latter causes a flexion of the levers and hence internal stresses in the levers.
Document WO2014/205816A1 discloses a control system for variable stator vanes for a turbomachine. Magnetic field sources actuate the vanes into different orientations.